<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <input type="text" id="username">
    <input type="checkbox" name="" id="remember">记住用户名
    <script>
        
        var username =document.querySelector('#username');
        var remember =document.querySelector('#remember');
        if(localStorage.getItem('username')){
            username.value = localStorage.getItem('username');
            remember.checked = true ;
        }
        remember.addEventListener('change',function(){
            if(this.checked){
                localStorage.setItem('username',username.value);
            }else{
                localStorage.removeItem('username');
            }
        })
    </script>
</body>
</html>